For billions of years, life on the planet Earth has evolved with about 12 hours of light and 12 hours of dark. We discovered fire a while ago, but have been using candles only about 5,000 years, and electric lighting for only about a century. This is what the country used to look like. Then 20 years later; 20 more years. And then, estimated, about 20 years in the future.

Our skies used to look like this. Now, they look like this. The photo on the left was taken during a blackout. These days, this is the only Milky Way our children will likely ever see.

But, so what? Does it have an effect on our health? (The light, not the candy bar.) Let’s find out. You may have heard that light at night increases breast cancer risk. Is this fact or fiction? Well, two reviews were published last year assessing the existing evidence. “Electric light causes cancer? Surely you’re joking.”

Well, let’s look at the evidence. Smack dab in the middle of our brain is the pineal gland, the so-called “third eye.” And it’s got only one function: produce melatonin in the dark. It’s hooked up to our eyes, and at dawn, the gland shuts down. Then at night, it turns back on. That’s how our internal organs know what time of day it is: they sense the level of melatonin in our bloodstream.
And melatonin is thought to suppress cancer growth, kind of like putting cancer to sleep at night.

Let’s test the theory. If that’s true, should blind women have more breast cancer, or less breast cancer? Less, right? Because their pineal gland never gets turned off by the sun. And guess what? Blindness is indeed protective against breast cancer. Cuts your risk in half.

What about shift workers who work in the middle of the night? Increased risk, right? Melatonin production is interrupted. What if you live in a neighborhood with really bright street lights? Increased risk; they took satellite photos, and the brighter neighborhoods seemed to correlate with greater breast cancer risk.

Anyway, fact—but what does this have to do with nutrition? Last year, for the first time ever, melatonin levels and food choices were studied. The Harvard Nurses’ Study found two foods significantly associated with melatonin suppression—like a bright light at night, which is bad. They looked at fruits, vegetables, nuts, bread, meat, and dairy. In which group were the offenders found?

Both meat and dairy intake were associated with lower melatonin levels, which may help explain why they found that meat and dairy intake in adolescence was associated with breast cancer risk later in life.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by veganmontreal.

For billions of years, life on the planet Earth has evolved with about 12 hours of light and 12 hours of dark. We discovered fire a while ago, but have been using candles only about 5,000 years, and electric lighting for only about a century. This is what the country used to look like. Then 20 years later; 20 more years. And then, estimated, about 20 years in the future.

Our skies used to look like this. Now, they look like this. The photo on the left was taken during a blackout. These days, this is the only Milky Way our children will likely ever see.

But, so what? Does it have an effect on our health? (The light, not the candy bar.) Let’s find out. You may have heard that light at night increases breast cancer risk. Is this fact or fiction? Well, two reviews were published last year assessing the existing evidence. “Electric light causes cancer? Surely you’re joking.”

Well, let’s look at the evidence. Smack dab in the middle of our brain is the pineal gland, the so-called “third eye.” And it’s got only one function: produce melatonin in the dark. It’s hooked up to our eyes, and at dawn, the gland shuts down. Then at night, it turns back on. That’s how our internal organs know what time of day it is: they sense the level of melatonin in our bloodstream.
And melatonin is thought to suppress cancer growth, kind of like putting cancer to sleep at night.

Let’s test the theory. If that’s true, should blind women have more breast cancer, or less breast cancer? Less, right? Because their pineal gland never gets turned off by the sun. And guess what? Blindness is indeed protective against breast cancer. Cuts your risk in half.

What about shift workers who work in the middle of the night? Increased risk, right? Melatonin production is interrupted. What if you live in a neighborhood with really bright street lights? Increased risk; they took satellite photos, and the brighter neighborhoods seemed to correlate with greater breast cancer risk.

Anyway, fact—but what does this have to do with nutrition? Last year, for the first time ever, melatonin levels and food choices were studied. The Harvard Nurses’ Study found two foods significantly associated with melatonin suppression—like a bright light at night, which is bad. They looked at fruits, vegetables, nuts, bread, meat, and dairy. In which group were the offenders found?

Both meat and dairy intake were associated with lower melatonin levels, which may help explain why they found that meat and dairy intake in adolescence was associated with breast cancer risk later in life.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by veganmontreal.

28 responses to “Melatonin & Breast Cancer”

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We know, based on studies of breast cancer risk due to exposure to ionizing radiation, for example, that since invasive breast tumors may take decades to manifest, dietary exposures during adolescence may be particularly important.

There are many links between meat and dairy consumption and breast cancer. However I think the most compelling is the link between dairy and breast cancer. In studying the geographical occurance of breast cancer, researchers have found that in places where dairy is not part of the average diet like Japan the incidence of breast cancer is very low. However they have also found that when Japanese women migrate to high dairy consumption countries like the US and adopt the countries diet their breast cancer risk becomes the same as the average population. The link can not be clearer. Do not put bovine breast milk into your body and reduce your breast cancer risk.

I agree that we were designed to be weaned from milk as toddlers (and stick to breasts of our own species) but the latest meta-analysis of prospective cohort studies did not find a convincing relationship between cow’s milk consumption and breast cancer:

I find that interesting, do you think that study is reliable? The study differentiates between dairy products and milk suggesting that dairy products, reduce breast cancer risk but Milk does not.

I know of several studies including the Harvard nurses study which show a link between meat and dairy consumption and breast and bowel cancers. Two areas of the body which are affected by hormones, which high fat diets seem to increase in women. As well as the hormones in cows milk itself.

There is also the research done by Dr T. Colin Campbell. Where he could turn on and off the cancer in rats by regulating the amount of casein in their diet.

It seems odd based on the number of studies I have seen sited that show a correlation that this study should find none.

It isn’t “a” study, but a meta-analysis, meaning it’s an attempt to pool the results of multiple studies together, in this case (as you can see in the above graphic) more than a dozen. After pooling the results from these studies they did not find that milk intake was significantly associated with breast cancer risk (in humans).

melatonin should be taken when needing to reset schedule from jetlag or some assistance falling asleep as we get older.
A reasonable does of melatonin is less than a milligram, 300-500 micrograms is best. If you’re taking 5mg, try to ramp down. our bodies only use approximately 300 micrograms to help us fall asleep, and supplement companies are selling much higher doses to avoid paying patent licensing fees, when it is in fact way too much.

Tart cherries have a high amount. But the best way to boost it is to get into a good sleep rhythm and to make sure your room is black when you sleep. Between 10pm and 2am is when the body produces a lot, so the earlier to bed, the better.

(Right now its midnight! What with electricity. computers and the internet, and a job that finished late, its hard to stick to early nights!!)

EMFs are also said to interrupt melatonin production, so if that were the case, it would be good to turn everything off and put cell phones in airplane mode.

I’ve been a full time night nurse for more than twenty years of my career. I am obese and I can’t help but notice that some of the others nurses are too. Until they realize my contribution to the team, the day staff think I (we) are fat because we must be lazy but I know I am definitely NOT lazy. I am awake during my nights off even if I am awake all day. I am close to retirement. I know there is a link between obesity and breast cancer (as well as ther types of cancer). What can I expect for my retirement in terms of sleep pattern changing back to the ‘norm’ and breast cancer risk?

Unfortunately, many of us ate the meat and dairy our parents fed us as adolescents. I am 39 and eating a whole foods plant based diet. But I know that my risk of breast and other cancers are still elevated. Are there any other protective measures that you recommend?

The only significant association was the lower morning melatonin levels found in red meat consumers. Dairy did not show a significant effect although dairy cream consumed by women subjects showed a minor association. Fish and poultry did not seem to have a lowering effect on the melatonin levels in the study. Very interesting study. I hope more are done on this interesting subject. The book, “Lights Out,” contains lots of information about lights at night effects on melatonin production for readers interested in this topic.

Can you make a video that discusses fluoride and its affect on the body, more specifically the pineal gland. I’ve heard the pineal gland referred to as the “third eye” and that it plays a huge role in our spiritual experiences. I was really hoping to hear your scientific reasoning on whether or not the pineal gland truly is as sacred as its been said to be. Also would like to know if fluoride in water, tooth paste, processed foods, etc causes calcification of the gland. If so, how do you prevent this, and what foods can de-calcify.

Whats with pineal gland and fluoride? Is fluoride harmfull melatonin and DMT production? I discovered that when I relax my body in meditation, esspecially in forehead region not only pain is going away, but experience itself is beeing altered plesantly. As Yogis say it is supposed to be an effect of DMT produced by pineal gland. Do You have some data about DMT production in our bodies? Have you been interested in meditation and it’s effects? Do You have some scientific data?

Hi Adrianne, I am one of the site moderators. Melatonin has been pretty extensively studied with virtually side effects other than people reporting they seemed to dream much more and some thought that was odd. Here is a journal article that discusses it’s efficacy. http://www.ncbi.nlm.nih.gov/pubmed/16423108 I hope this is helpful.

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